定语从句就是用来修饰名词或代词的一个具有的完整主谓结构的句子.定语从句分为非限制性和限制性，非限制性定语从句一定不能用that引导。

1. 理解定语的关键是先找到先行词，先行词一般是一个单词或短语，但在复杂的长难句中，先行词往往是一个分局，这时的定语从句用which 或as As is so often pointed out,knowledge is a two-edged weapon which can be used equally for good or evil.正如人们常常指出的，知识是一把双刃剑，可以用于造福，也同样可以用来危害（as 引导的非限制性定语从句）

2. as 引导限制性定语从句和非限制性定语从句有着根本的不同。前者只用在一些固定结构如，such,the same,as 修饰的先行词后，而后者则没有这些限制，且位置很灵活，可以用于句首，句中，句末。

Straford-on-avon, as we all know,has only one industry 众所周知，埃文河畔的斯特拉福德只有一种行业

3. 复杂定语从句中，先行词和关系词有时被分隔开，这就需要正确理解定语从句本身的意思，然后根据从句的意思来找能与其构成逻辑语义联系的先行词。

It can be predicted, however,that from time to time questions will arise which will require specific scientitic answers.不过，可以预见的是，将来会经常有问题出现，需要科学给出特定的答案。（为保持句子的平衡，修饰questions的定语从句放到谓语后）

4. 完形填空中有时可能考关系词的选用，这就要求考生知道关系词在从句中充当什么句子成分然后来决定选用哪一个关系词。看看下面两句中先行词都是表示时间的名词，该用什么关系词。 I never forget the time ____(which,when)I spent on campus. 我永远不会忘记在大学校园里度过的时光。选择关系词要看定语从句中缺少什么成分，该句中缺少spend的宾语，所以选which。I never forget the day___(when,which)we first met in the park.我永远不会忘记我们第一次在公园见面的情景 该句的从句中缺少时间状语，所以选用when

5. 关系词前面介词的理解一是要注意根据定语从句中的动词，形容词，名词来

判断，一般都是这些词的固定搭配。二要注意与先行词密切相关，有些是与先行词构成固定搭配。We assume that the meaning of these underwater sounds are similar to those with which we are familiar on land 据我们猜测，这些水底声音的意义同我们所熟悉的陆地上的声音相似 be familiar with 是固定搭配the method of scientific investigation is simply the mode by which all phenomena are reasoned about and given precise and exact explanations 科学研究的方法不过是人类思维活动的必要表达方式，也就是对一切现象进行思索并给与精确而严谨解释的表达方式 先行词mode的搭配介词by

6. 区分when,where引导的定语从句和when,where引导时间或地点的状语从句：这两个关系副词引导的定语从句时，前面必然有表示时间或地点的名词 （先行词）approximately 45% of the world’s population live in the climate zone where mosquitoes transmit malaria=…live where mosquitoes transmit malaria 第一句where从句作定语，而第二局做状语

7. that 引导的定语从句和同位语从句区别：that 在定语从句中必须担当成分（关系代词），而在同位语从句 不做成分（连词）the news that the leader will come here is not true 同位语the news that you told me last week is not true 定语从句在从句中充当told的宾语.

 

第二篇：定语从句语法总结

在复合句中修饰名词或代词的从句叫定语从句

e.g. I like music

Music 是先行词，that是关系代词

He is the man

Man是先行词，who是关系代词

1. who / that 在定语从句中做主语时，

谓语动词的单复数应与先行词保持一致

I prefer shoes that are cool.

I like a pizza that is really delicious.

I love singers who are beautiful.

I have a friend who plays sports.

2. ( who 和that 引导定语从句作主语 不可省略）

The old man is a professor. He teaches chemistry in a college.

The old man is a professor who teaches chemistry in a college.

The old man is a professor that teaches chemistry In a college.

3. (which 和that 引导定语从句作宾语 可省略）

I enjoyed reading the book. You gave me the book.

I enjoyed reading the book you gave me .

4. (whose 在定语从句中作定语用）

What?s the name of the man? His sister is a doctor.

What?s the name of the man whose sister is a doctor?

Have you seen the cup? Its color is red.

Have you seen the cup whose color is red?

5. when 在定语从句中作时间状语

I?ll never forget the day . I first came to Beijing.

I?ll never forget the day when I first came to Beijing

6. where 在定语从句中作地点状语

This is the cinema. I watched Harry Potter last month in it.

This is the cinema where I watched Harry Potter last month.

注意：（1）当定语从句中含有介词，介词放在句末时，who， that， which可省略，但介词在关系代词前时，只能用“介词+which/whom”结构。例如：

This is the house in which we lived last year.

这是我们去年居住的房子。

Please tell me from whom you borrowed the English novel.

请告诉我你从谁那借的这本英文小说。

（2）含有介词的固定动词词组中，介词不可前置，只能放在原来的位置上。 例如：This is the person whom you are looking for.

这就是你要找的那个人。

a. 先行词被序数词或形容词最高级所修饰，或本身序数词、基数词、形容词最高级时，

只能用that，而不用which.例如：

He was the first person that passed the exam.

他是第一个通过考试的人。

b. 被修饰的先行词为all， any， much， many，everything， anything， none， the one等不定代词时，只能用that，而不用which.例如：

Is there anything that you want to buy in the shop？

你在商店里有什么东西要买吗

c.先行词被the only， the very， the same， the last，little， few 等词修饰时，只能用that，而不用which.

例如：This is the same bike that I lost.

这就是我丢的那辆自行车。

d. 先行词里同时含有人或物时，只能用that， 而不用which.例如：

I can remember well the persons and some pictures that I saw in the room.

我能清楚记得我在那个房间所见到的人和一些照片。

e.以who或which引导的特殊疑问句，为避免重复，只能用that.例如：

Who is the girl that is crying？

正在哭泣的那个女孩是谁？

f. 主句是there be 结构，修饰主语的定语从句用that，而不用which.例如：

There is a book on the desk that belongs to Tom. 桌子上那本书是汤姆

（5）关系词只能用which，而不用that 的情况：

a.先行词为that， those时，

What?s that which is under the desk？

b.关系代词前有介词时，例如：

This is the room in which he lives.

c.引导非限制性定语从句，例如：

Tom came back， which made us happy. 汤姆回来了，这使我们很高兴。

限制性定语从句紧跟先行词，主句与从句不用逗号分开，从句不可省去，非限制性定语从句主句与从句之间有逗号分开，起补充说明作用，如省去，意思仍完整。